Due to wide distribution of mobile terminals and tablet PCs and rapid advancement of mobile computing based on wireless internet technologies, innovative increase of wireless network capacity is being demanded.
Currently, although a 4th generation mobile communication system, Long Term Evolution (LTE) system, has been world-widely commercialized and it can provide a higher throughput than the 3rd generation mobile communication systems, it is still difficult to accommodate rapidly-increasing mobile data.
In many studies, it is predicted that traffic amount of mobile users will increase rapidly. An adoption of a new advanced physical layer technology or allocation of additional spectrums is being considered as the representative solutions to satisfy the above rapid explosive increase of traffic amount. However, the physical layer technologies are already approaching their theoretical limits, and allocation of additional frequency spectrum also cannot be a fundamental solution for capacity expansion of cellular networks.
Therefore, demands for technologies, which can increase capacity of a wireless network by hierarchically deploying small cells in sites having much traffic requirements and enabling close cooperation between macro base stations and small cell base stations, are increasing.
In a 3rd Generation Partnership Project (3GPP) standardization organization standardizing Long-Term Evolution (LTE), in order to efficiently accommodate rapidly-increasing data traffic requirements, the standardization on technologies for small cell enhancement (SCE) is going on.
However, only an initial discussion on the cell discovery has been made until now, and specified and efficient methods for the cell discovery have not been proposed yet.